We have developed techniques to biochemically screen large numbers of clones. The techniques have been successfully applied to the isolation of 10 mutant strains affecting N-acetylglucosanimidase in Dictyostelium discoideum. Four of these strains form thermolabile enzyme. The enzyme is essential for normal migration in this organism as shown by the impaired migration in the mutant strains. Other stage specific enzymes accumulate normally in the mutant strains. We plan to construct diploids from the mutant strains and with the wild-type to test for complementation and dominance, respectively. We will extend this approach to study mutations in other stage specific enzymes including Beta-glucosidase, alpha-mannosidase, alkaline phosphatase and UDPG pyrophosphorylase. We have been successful in isolating mutants affecting two of these enzymes already and are optimizing screening proceedures for the other two now.